Thermostatic finger-piece for push-buttons.



NO MODEL.

WITNESSES:

PATENTED 001?. 4, 1904.

W. E. HARMON.

THERMOSTATIC FINGER PIECE FOR PUSH BUTTONS.

APPLIOATION FILED 1930.26, 1903.

INVE'NTOR: Mil/S mm,

Patented October I, i0 1.

UNITED STATES PATENT OFFICE.

IVILLIS E. HARMON, OF MECHANIC FALLS, MAINE.

THERIVIOSTATIC FINGER-PIECE FOR PUSH-BUTTONS.

SPECIFICATION forming part of Letters Patent No. '771,54='7,clatedOctober 4, 1904. Animation filed December 26,1903. Serial No. 186,572.(No model.)

To aZZ whom it may concern.-

Be it known that I, IVILLIS E. HAnMoN, a citizen of the United States,residing at Mechanic Falls, in the State of Maine, have invented certainnew and useful Improvements in Thermostatic Finger-Pieces forPush-Buttons, of which the following is a specification, reference beinghad to the accompanying drawings.

My invention relates to a thermostatic finger-piece for an electricpush-button attachment, whereby upon any undue rise of the temperatureof the room in which the attachment is situated the electric circuitwill be antomatically closed and a corresponding inclication made uponthe annunciator with which the push-button attachment is connected.

In my device the entire thermostatic element is comprised within thefinger-piece of the push-button, the contact-points and the containingdevice being similar to the corresponding parts of the ordinary standardconstruction of push-button attachments. Consequently by the use of myinvention it is possible to introduce my thermostatic finger-piece intobuildings or establishments already fitted with push-buttons andannunciators without any other change than the substitution offinger-pieces embodying my invention for those already in place in thepush-button attachments.

In devices of this character heretofore described the fusible piece,upon the melting of which the automatic operation of the device depends,has been inserted in such relation to the other parts that it must atall times support or resist the entire thrust of the spring inclosed inthe finger-piece. This spring must have considerable strength, andconsequently if the piece softens slightly, as it occasionally will at alower temperature than that which it is intended should cause theattachment to operate, there is a gradual dislocation or extension ofthe spring and soon an improper operation of the device. This is veryobjectionable. I haveovercome these objections.

To this end my invention consists, primarily, in inserting a coiledspring Within the fingerpiece and providing connections including acatch and fixed resistance-point by engagement of which the main thrustof the spring is resisted and a fusible plug by which the catchand'resistance-point are held in engagement, by means of Which atordinary temperatures the spring is held retracted under compressionwithin the finger-piece, while upon any undue rise of the temperaturethe dissolution of the fusible plug suffers the catch to becomedisengaged and allows the spring to be projected from the botton of thelinger-piece, thus efiecting the closing of the electric circuit in thesame way as when the push-button is operated manually.

In the accompanying drawings, Figure I is a central section of apush-button attachment embodying my invention, the parts being in theirnormal position. Fig. II is a similar section showing the changedrelation of the parts upon the melting of the fusible plug. Fig. III isan elevation of the finger-piece embodying my invention as seen byitself. Fig. IV is a central section of a modified form of finger-pieceembodying my invention.

In the following specification and claims I shall use the termpush-button attachment to cover the entire device, which is usuallyspoken of as a push-button that is to say, the contact-points, thecasing within which they are mounted, and the push-button orfinger-piece by which the motion of the contact-points to close thecircuit is effected. This latter element for the sake of cleardistinction I am herein designating as the fingerpiece.

In the accompanying drawings the casing consists of the shell 1 and thebase 2. The top of the shell is centrally perforated, so as to sustainand guide the flanged push-button 3. Mounted upon the base are the twocontactpoints a and 5 in the form of resilient metallic strips the freeends of which normally assume the position shown in Fig. I, where theyare sufficiently separated to break the electrical circuit of which theyform a part, but sufficiently close to each other for a slight pressurefrom the finger-piece above them to bring them into contact and closethe circuit. \Vith some slight variation this is the arrangement of thecontact-points 1n the standard pushbutton attachments ordinarily used.

Thefinger-piece consists of an external cylinder 6, provided at thebottom with a flange 7. This cylinder is turned in at the top, so as toform a second or internal cylinder 8, with an annular space between thetwo. Within this annular space is situated the coiled spring 9.

10 is a separable bottom for the finger-piece resting within the outercylinder 6 in contact with the" lower end of the inner cylinder. Thisbottom is fitted with a central spindle 11, having a projecting catch 12at the upper end.

13 is a fixed resistance-piece in the shape of a lug or flange upon theinside of the inner cylinder projecting sufliciently to engage the catch12 when the spindle 11 is placed in the central or upright position.(Shown in Fig.1.) Of the engaging surfaces of the catch andresistance-piece one (in this case the catch) is inclined or beveled, sothat the engagement is released if the catch is free to move sidewise,but otherwise maintained against encl- Wise thrust by the spring. Inthis position the bottom 10 is in place and the spring 9 compressed.WVhile the parts are in this position, a plug of fusible material is runinto the interior of the internal cylinder and allowed to set therein.It thus. binds the parts in the position shown, the effective portionbeing that which is interposed between the side of the spindle 11 backof the catch and the opposing side of the inner cylinder 8. Both theinner and outer cylinders may be perforated with small holes, the formof perforations of the outer cylinder being shown in Fig. III, for thepurpose of increasing the readiness with which the fusible plug withinthe fingerpiece is afl'ected by the temperature of the surrounding air.

In operation any undue rise in this tem perature above that which is tobe ordinarily expected and provided for effects the melting of thefusible plug, allowing the spindle 11 to move sidewise, and thusdisengage itself from the lug 13, whereupon the spring forces theseparable bottom of the finger-piece down and accomplishes the closingof the circuit just the same as though the push-button had been pressedby hand. I

In Fig. IV, I have shown a varying construction of the finger-piece. Thecylinder here consists of a single shell 14, provided with a flange 15.16 is the separable bottom, fitted, as above, with a spindle 17 and acatch 18. Near the top of the cylinder there is provided a slotteddiaphragm 19, through which the end of the spindle projects. 20 is aresistance-piece with which the catch 18 engages, as shown in thedrawings, when the spindle occupies its central position. 21 is thespring interposed between the bottom of the cylinder and the diaphragm.The fusible plug or compound occupies the entire space above thediaphragm and holds the parts in the position shown; but as soon as theplug melts the end of the catch of the spindle is free to disengageitself from the lug by a sidewise motion, which it is permitted to takeby reason of the length of the slot in the diaphragm. I

In all cases the essential feature of my invention is the springnormally compressed within the finger-piece and which by its projectionwhen the fusible plug melts presses the ordinary contact-pieces of theattachment together, and the catch with a fixed resistancepoint, byengagement of which the thrust of the spring is at all times resisteduntil the melting of the plug permits a sidewise movement of the catch.It will be observed that owing to the simplicity of this arrangement thefinger-piece occupies very little space and need be no larger than theordinary porcelain or ebonite buttons employed in the common form ofpush-button attachments, for which it may in every case be substituted,with the result of converting the push-button system into one afiordingthe additional protection of a thermostat in every room in whichattachments are situatedthat is to say, the finger-piece is universal inits nature, by which I mean that it is interchangeable with the ordinaryfingerpiece.

I claim 1. A thermostatic finger-piece for a pushbutton attachmentcomprising a cylindrical shell; a spiral spring within said shell;aseparable bottom for the shell; a spindle within said shell attached tothe separable bottom; a catch on the spindle; a fixed resistance-pieceon the inside of the shell which when in engagement with the catch onthe spindle opposes the thrust of the spring; and a fusible plug wherebythe catch and resistance-piece are normally held in engagement,substantially as described.

2. A thermostatic finger-piece for a pushbutton attachment comprising acylindrical shell; a spiral spring within said shell; a separable bottomfor the shell; a spindle within said shell attached to the separablebottom; a catch on the spindle; a fixed resistance-piece on the insideof the shell which when in engagement with the catch on the spindleopposes the thrust of the spring; an inclined edge on one of theengaging surfaces of the catch and resistance-piece; and a fusible plugwhereby the catch and resistance-piece are normally held in engagement,substantially as described.

3. A thermostatic finger-piece for a pushbutton attachment comprising acylindrical shell; a spiral spring within said shell; a separable bottomfor the shell; a spindle within said shell attached to the separablebottom; a catch on the spindle; a fixed. resistance-piece on the insideof the shell which normally engages the catch on the spindle and opposesthe thrust of the spring; and a fusible plug inserted between the sideof the spindle back of the catch and the opposing side of thecylindrical shell, which when it melts allows a sidewise movement of thespindle to permit it to disengage the resistance-piece, but which untilit melts maintains them in engagement, substantially as described.

i. A thermostatic finger-piece for a pushbutton attachment comprising acylindrical shell; a slotted partition dividing the shell horizontallyinto two compartments; a spiral spring in the lower compartment of saidshell; a separable bottom for the same; a spindle attached to theseparable bottom, and extending up through the slotted partition; acatch on the spindle above the slotted partition; a resistance-piece inthe upper compartment

